We are currently studying the role of norepinephrine and dopamine containing neurons in the regulation of LH and prolactin secretion. Dopamine receptors involved in the inhibition of prolactin secretion show denervation supersensitivity. Anterior pituitary glands from long and short term denervated animals will be incubated with apomorphine, to determine if the dopamine receptors involved are in this tissue. Estrogen potentiates prolactin release in response to handling stress or the blockade of dopamine synthesis with alpha-methyl-p-tyrosine. A portion of estrogen effect was at the level of the anterior pituitary, since a greater prolactin response was found to a TRH challenge. We are currently testing whether the action of estrogen at the level of the anterior pituitary involves a dopamine receptor. The catechol-o-methyl transferase radioenzymatic assay was used to quantitate levles of norepinephrine and dopamine at 1000 and 1700 hr. on diestrus 1 and proestrus. The arcuate, ventromedial, suprachiasmatic, medial preoptic nuclei and the median eminence were microdissected using the Palkovits technique. A three fold increase in norepinephrine was observed in the suprachiasmatic nuc. only coincident with the ovulatory surge. We are currently studying if this change occurs during induced LH surges in ovariectomized rats with silastic implants of estradiol. BIBLIOGRAPHIC REFERNCES: Schechter, J., B. Yancy and R.I. Weiner. 1975. Response of tanycytes of rat median eminence to intraventricular administration of colchicine and vinblastine. Anatomical Record, 184: 233-250. Selmanoff, M.K., R. Weiner, L.D. Brodkin and P.K. Siiteri. 1976. Conversion of androgens in discrete hypothalamic and limbic regions of the rat. Fed. Proc., 35:685 (abst).